1. Field of the Invention
The present invention relates to image correction of color image.
2. Description of Prior Art
In an image processor, a color image is generally subjected to image correction. Various types of correction such as color balance control or color correction are performed.
Color fog is a phenomenon where a particular color covers an image so as to degrade color balance. In a typical example, it is observed when an object is captured under a fluorescent light without using a strobe light. Color fog is observed in many situations.
In order to recover normal color balance, it is known in image processing to convert the brightest portions to white and the darkest portions to black. This technique is simple, but effective. However, in many exceptional cases it may cause a reverse effect or has no effect.
In some image processing, color fog may be checked automatically at a step before the correction. However, when colors are checked automatically, erroneous decisions happen for an image such as a sunset scene or a photograph adopting intentional color representation.
In prior art image correction, contrast is corrected first, and color balance is adjusted next. In many cases, color balance can be adjusted mainly by correcting only contrast. Then, color balance is adjusted in an interactive way to a degree that the color balance is not anomalous when viewed with eyes. It is desirable that an image can be corrected automatically. However, there remain many problems on automatic processing.